导　　师： 沙学军

学科专业： 0810

授予学位： 硕士

作　　者： ;

机构地区： 哈尔滨工业大学

摘　　要： 空天网络是包括高空平台、中低轨卫星、静止轨道卫星在内的综合空间通信网络，具有通信覆盖范围广、频谱资源丰富和不受地形条件限制等优点，适用于全球范围内通信和紧急通信等场景。利用空天网络进行可靠业务传输的需求日益增加。如何针对空天网络设计一套可靠的高效的同时又能保证各连接传输公平性协议成为研究的热点。TCP是地面网络应用最为广泛的可靠传输协议，并且在地面网络中具有很高的TCP传输效率。但是，相对于传统的地面网络来说，空天网络传输时延长，链路误码率高，星上处理资源受限，这些特性使得在空天网络中进行可靠传输面临传输效率低下和带宽分配不公平问题。因此，本文根据空天网络的特点，针对现有的TCP拥塞控制算法进行优化改进使之能够适应空天网络，提高传输层的传输效率并保证传输公平。 本文针对现有的提高TCP传输效率的研究成果的不足，结合空天网络的特点，分别设计了基于预测调整的慢启动和丢包区分的拥塞控制算法。基于预测调整的慢启动算法的设计思想是在慢启动开始阶段采用较大的发送窗和增长速度以及合理的慢启动阈值。随着发送窗口的增长，根据当前的可用带宽以及所处的慢启动阶段对发送窗口进行相应的调整，使之能够快速而平稳地进入拥塞避免阶段。此外，对于空天网络的高误码环境带来的传输效率低下问题。本文结合ECN和RED，根据发送端接收到ACK的种类及数量进行丢包和拥塞区分，算法实现简单，可以很好地对拥塞和误码进行区分，使发送窗口快速达到并稳定在较高的发送速率，从而提高传输效率。 同时，空天网络中存在长短时延业务共享瓶颈链路情形，此时，短时延业务竞争带宽能力强，长时延业务竞争带宽能力差，最终造成带宽分配不公。因此 Aerospace network is a integrated space communications network, includingaerial platforms, LEO and MEO satellites, geostationary satellites, which has a widerange of communications coverage, rich spectrum resource and not the terrainconditions, etc., suitable for some scenes such as worldwide communications andemergency communications. The demand for reliable transport service with aerospacenetwork is increasing. To design a network for aerospace reliable and efficienttransmission protocol while ensuring the fairness of the agreement each connectionhas become a hot research.TCP is the most widely used ground network reliabletransmission control protocol and TCP transport with high efficiency in terrestrialnetwork. However,compared with the traditional terrestrial networks, aerospacenetwork has long round trip delay, high link error rate, limited processing resourceswith the satellite. All these features make the aerospace network faces tra nsmissioninefficiencies and bandwidth allocation inequities for reliable transport network.Therefore, according to the characteristics of aerospace network, for the existingTCP congestion control algorithm is optimized so that it can adapt to improve a ir andspace network, improving transmission efficiency and to ensure the transmissionfairness of the transport layer. In this paper, with the lack of existing research of improving the efficiency ofTCP transmission, combined with the characteristics of aerospace network, wedesigned slow start algorithm based on the forecast revision and packet lossdiscrimination algorithm. The design idea of slow start algorithm based on thepredicted and adjusted is to start slow start phase with a larger growth rate of thecongestion window and a more reasonable threshold. With the growth of thecongestion window, based on the current available bandwidth and slow start phase inwhich the congestion window is adjusted accordingly, so that it can quickly andsmoothly into the congestion avoidance phase. In addition, the high error aerospacenetwork

关 键 词： 拥塞控制 空天网络 传输效率 公平

领　　域： [电子电信] [电子电信]